Through-silicon via (TSV) fabrication consists mainly of the following steps: etching, deposition of insulator, deposition of barrier and seed layers, and electrochemical plating. Depending on the application, the TSV structures differ in size, aspect ratio, density, materials, and technology. Each application has its own requirements which affect the whole processing scheme. The most important parameters for TSV fabrication are aspect ratio and contact density. Their values are specific to each application. In this chapter, we present a specific process flow for a TSV—interposer realizing through holes down to a diameter of 10 m. The fabrication of interconnect is carried out as a through-hole connection. In contrast to the blind hole via integration schemes, the TSVs are etched through to an etch-stop layer. Thus, no grinding, polishing, or etch back processes have to be applied later as it is required in blind hole via integration schemes. Since the fabrication aims at interposer fabrication, no active devices and thus, no restrictions in the thermal budget have to be considered. The complete process flow consists of the following steps and is schematically pictured in Fig. 2.1:
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